This program examines the communication of cells with extracellular matrices. It is a close collaboration among investigators whose specialties range from cell and molecular biology to crystallography and NMR. In the project this wide range of expertise is brought to bear on the molecular mechanisms of cell-matrix recognition. The work centers around the RGD cell adhesion sequence originally discovered under this grant and its recognition by integrins. Peptide display libraries will be used as a source of peptides that will mimic the integrin-binding site in integrin-ligand interaction, the binding of the alpha5beta1 integrin to fibronectin, in particular. Physical methods will be applied to the study of the integrin-binding portions of fibronectin and the fibronectin- binding portions of the receptor for fibronectin. The integrin-binding will be related interactions between various parts of fibronectin that may compete with the integrin-binding. These studies will provide new information on integrin-ligand interactions and may help in the design of improved probes for the roles of integrins in malignancies and other diseases.